During injury, invasion of pathogens, or other forms of tissue damage, higher vertebrates implement a cascade of biochemical, immune and inflammatory reactions collectively termed the acute phase response. The inflammation results in an increase in blood flow and the delivery of important factors to the affected site. These factors act to limit microbial growth, reduce tissue damage, and aid in the removal of damaged tissue. The acute phase response is a primitive, nonspecific mechanism which reacts quickly prior to the development of the specific processes of humoral and cellular immunity.
C-reactive protein (CRP) has long been recognized as an important acute phase response protein, and its concentration in serum may increase as much as 1,000-fold during the acute phase response. CRP is a pentamer consisting of five identical subunits, each having a molecular weight of about 23,500. The pentameric form of CRP is sometimes referred to as "native CRP."
In about 1983, another form of CRP was discovered which is referred to as "modified-CRP" or "mCRP." The formation of mCRP from native CRP involves the dissociation of native CRP into its subunits which also undergo a change in conformation. As a result, mCRP expresses antigenicity which is distinct from that of native CRP (referred to as "neo-CRP antigenicity"), and antibodies are available which can distinguish mCRP from native CRP (see, e.g., U.S. Pat. No. 5,272,258 and Potempa et al., Mol. Immunol., 24, 531-541 (1987)). The conversion of native CRP into mCRP is irreversible (the subunits do not reassemble into native CRP). Kresl et al., Int'l J. Biochem. Cell Biol., 30, 1415-1426 (1998).
It has been reported that mCRP can influence the development of monocyte cytotoxicity, improve the accessory cell function of monocytes, potentiate aggregated IgG-induced phagocytic cell oxidative metabolism, and increase the production of interleukin-1, prostaglandin E and lipoxygenase products by monocytes. Potempa et al., Protides Biol. Fluids, 34, 287-290 (1987); Potempa et al., Inflammation, 12, 391-405 (1988); Potempa et al., Proc. Amer. Acad. Cancer Res., 28, 344a (1987); Chu et al., Proc. Amer. Acad. Cancer Res., 28, 344a (1987); Zeller et al., Fed. Proc., 46, 1033a (1987); Chu et al., Proc. Amer. Acad. Cancer Res., 29, 371a (1988). It is also known that mCRP can be used to treat viral infections, bacterial infections, endotoxic shock and cancer. See U.S. Pat. Nos. 5,283,238, 5,405,832, 5,474,904, and 5,585,349. It is further known that mCRP stimulates thrombocytopoiesis and the maturation of megakaryocytes and that it can be used to treat thrombocytopenia. See U.S. Pat. No. 5,547,931. Finally, it is known that mCRP binds immune complexes and aggregated immunoglobulin and can, therefore, be used to remove immune complexes and aggregated immunoglobulin from fluids and to quantitate immune complexes. See U.S. Pat. No. 5,593,897. It should be noted that mCRP differs from native CRP in its biological activities. See, e.g., the patents listed above.